Firas abu jaber

An-Najah National University
Faculty of Graduate Studies
New Routes for Synthesis of Environmentally Friendly
Superabsorbent Polymers
By
Firas Jaber Abd Alateef Abu Jaber
Supervisor
Dr. Othman Hamed
This Thesis is Submitted in Partial Fulfillment of the Requirements for
the Degree of Master of Science in Chemistry, Faculty of Graduate
Studies, An-Najah National University, Nablus, Palestine.
2012

III
DEDICATION
To my father, my mother, my brothers, my sisters,
and to all my friends

IV
ACKNOWLEDGMENT
Praise and thanks to Allah, the most merciful for assisting
and directing me to the right path. Special thanks to my
research supervisor Dr. Othman Hamed for the chance given
me to work with his research group. I am deeply grateful to
him for his constant presence, and his encouragement
throughout this research project.
Great thanks to Dr Kamel Odwan for helping me in studying
the bacterial activity. My thanks to the thesis committee
members for their willingness to read the thesis and provide
useful suggestions.
Many thanks to Mr. Omair Nabulsi, the chemistry labs
supervisor at An- Najah National University. Special thanks
to Dr.Haytham Saadi of the Jordan University for his
cooperation and support.
I am indebted to many of my colleagues who supported me:
Marwan , Ammar and all my friends. Also I will never forget
the support of my students.

V
‫اإلقرار‬
‫أنا‬‫الموقع‬‫أدناه‬‫مقدم‬‫الرسالة‬‫التي‬‫تحت‬‫ان‬‫و‬‫عن‬:
‫لتحضير‬ ‫جديدة‬ ‫طرق‬‫للبيئة‬ ‫صديقة‬ ‫االمتصاص‬ ‫فائقة‬ ‫ات‬‫ر‬‫بوليم‬
‫اقر‬‫بأن‬‫ما‬‫اشتملت‬‫عليه‬‫الرسالة‬‫إنما‬‫هي‬‫من‬‫إنتاجي‬‫الشخصي‬‫باستثناء‬‫ما‬‫تمت‬‫ة‬‫ر‬‫اإلشا‬‫إليه‬
‫حيثما‬‫ورد‬،‫ان‬‫و‬‫الرسالة‬‫ككل‬،‫أو‬‫أي‬‫ء‬‫جز‬‫منها‬‫لم‬‫يقدم‬‫من‬‫قبل‬‫لنيل‬‫أية‬‫درجة‬‫علمية‬‫أوبحث‬‫علمي‬
‫أو‬‫بحثي‬‫لدى‬‫أية‬‫مؤسسة‬‫تعليمية‬‫أو‬‫بحثية‬‫ى‬‫أخر‬.
Declaration
This work provided in this thesis, unless otherwise referenced, is the
researcher's own work, and has not been submitted elsewhere for any other
degree or qualification.
‫الطالب‬ ‫اسم‬:Students name
‫التوقيع‬:Signature :
‫التاريخ‬:Date:

VI
List of Contents
No. Contents Page
Dedication III
Acknowledgment IV
Declaration V
List of Contents VI
List of Tables IX
List of Figures X
List of Graphs XIII
List of Appendices XIV
Abstract XVI
Chapter One: Introduction
1.1 Background 1
1.2 Superabsorbent Polymers Physical Shapes 3
1.3 Water Absorbents 5
1.4 Applications 6
1.5 History and Market 6
1.6 Types of Superabsorbent Polymers and Methods of
Preparation
8
1.6.1 Nonionic Polymer 8
1.6.1.1 Polyacrylamide 13
1.6.1.2 Polyvinyl Alcohol 14
1.6.1.3 Polyethylene Oxide 14
1.6.2 Natural Polymer 15
1.6.2.1 Anionic Superabsorbent Polymers 16
1.6.2.2 Monomers for Acrylic Anionic Polymers 17
1.7 Preparation of Superabsorbent Polyacrylates 20
1.8 Superabsorbent Polymers Origins 22
1.9 Polysaccharide-based Superabsorbent Polymers 23
1.9.1 Preparation of Superabsorbent polymer based
polysaccharides by graft polymerization
24
1.9.2 Preparation of Superabsorbent polymer based
polysaccharides by cross-linking
25
1.10 Polyamino Acid - based Superabsorbent Polymers 29
1.11 Importance of Biodegradable Superabsorbent Polymers 30
1.12 Bio-Degradability versus chemical structure 32
CHAPTER TWO: EXPERIMENTAL
2.1 Preparation of Allyl sucrose 37
2.2 Preparation of Epoxy allyl sucrose 40
2.3 Preparation of Superabsorbent polymers – Method A 42

VII
2.3.1 Superabsorbent polymer cross-linked with Allyl sucrose 42
2.3.2 Superabsorbent polymer cross-linked with Epoxy allyl
sucrose
43
2.3.3 Superabsorbent polymer cross-linked with 1,4-Butanediol
diglycidyl ether
43
2.3.4 Superabsorbent polymer cross-linked with Ethylene
glycol diacrylate
43
2.4 Preparation of Superabsorbent polymer – Method B 44
2.4.1 Superabsorbent polymer cross-linked with Allyl sucrose 44
2.4.2 Superabsorbent polymer cross-linked with Epoxy allyl
sucrose
44
2.4.3 Superabsorbent polymer cross-linked with 1,4-Butanediol
diglycidyl ether
45
2.4.4 Superabsorbent polymer cross-linked with Ethylene
glycol diacrylate
45
2.5 Tea- bag Method 45
2.5.1 Tea bag test in water 46
2.5.2 Tea bag test in saline solution (0.9 %) 47
2.6 Absorbency Under Load (AUL) 49
2.7 pH Neutrality after swelling in water 52
2.8 Rewetting of Superabsorbent polymer in water 53
2.9 Rewetting of Superabsorbent polymer in saline 53
2.10 Polymer Extracts 45
2.11 Biodegradability 55
2.11.1 Test Microorganisms 55
2.11.2 Biodegradation Experiments 55
CHAPTER THREE: RESULTS AND DISCUSSION
3.1 Monomer Characterization 61
3.1.1 1
H-NMR Spectroscopy of Allyl sucrose 61
3.1.2 C-13 NMR Spectroscopy of Allyl sucrose 62
3.1.3 1
H-NMR Spectroscopy of Epoxy allyl sucrose 62
3.1.4 C-13 NMR Spectroscopy of Epoxy allyl sucrose 63
3.2 Discussion of prepared Polymers 64
3.2.1 Polyacrylic acid cross-linked with Allyl sucrose 64
3.2.2 Polyacrylic acid cross-linked with Epoxy allyl sucrose 66
3.2.3 Polyacrylic acid cross-linked with 1,4-Butanediol
diglycidyl ether
67
3.2.4 Polyacrylic acid cross-linked with Ethylene glycol
diacrylate
68
3.3 Polymer Analysis 70

VIII
3.3.1 Infrared Spectra (IR) Results 70
3.3.2 DSC Results 71
3.3.3 Morphological Analysis 71
3.3.4 Superabsorbent Polymer Absorbency 73
3.3.5 Rewetting of Superabsorbent polymers 78
3.3.6 pH Neutrality of Superabsorbent polymers after swelling
in water 4% cross-linking
78
3.3.7 Thermal stability of prepared Superabsorbent polymers 79
3.3.8 Polymer Extracts 82
3.4 Biodegradability 83
CONCLUSION 85
References 86
Appendix 96
‫الملخص‬ ‫ب‬

IX
List of Tables
No. Table Page
1.1 Comparison between the absorbing capacity of
common materials with SAP
3
2.5.1.1 Free swell results of Superabsorbent polymer cross-
linked with Allyl sucrose
46
linked with Epoxy allyl sucrose
46
linked with 1,4-Butanediol diglycidyl ether
46
linked with Ethylene glycol diacrylate
47
linked with Allyl sucrose
47
linked with Epoxy allyl sucrose
48
linked with 1,4-Butanediol diglycidyl ether
48
linked with Ethylene glycol diacrylate
49
2.6.1 Absorbency under load results of Superabsorbent
polymer cross-linked with Allyl sucrose
51
polymer cross-linked with Epoxy allyl sucrose
51
polymer cross-linked with 1,4-Butanediol diglycidyl
ether
52
polymer cross-linked with Ethylene glycol diacrylate.
52
2.7 pH of Superabsorbent polymers 53
2.10 Percentage of Superabsorbent polymer extracts 54
3.3.4.1 Absorbency of SAP cross-linked with Allyl sucrose 74
3.3.4.2 Absorbency of SAP cross-linked with Epoxy allyl
sucrose
75
3.3.4.3 Absorbency of SAP cross-linked with Ethylene glycol
diacrylate
76
3.3.4.4 Absorbency of SAP cross-linked with 1,4-Butanediol
diglycidyl ether
77
3.3.6 pH of prepared superabsorbent polymers 79
3.3.8 SAP extract in prepared polymers 82

X
List of Figures
No. Figure Page
Fig.1.1 (i) A visual comparison of the SAP single particle in
dry (right) and swollen state (left). (ii) A schematic
presentation of the SAP swelling
2
Fig.1.2.1 Cellulose polymer cross-linked with
epichlorohydrin
4
Fig. 1.2.2 Structures of some of the cross linking-agents 5
Fig.1.5.1 Superabsrobent polymer made from acrylic acid and
divinylbenzene
7
Fig.1.5.2 Superabsrobent polymer made from Starch grafted
polyacrylonitrile
7
Fig.1.6.1.1 Example on nonionic water soluble superabsorbent
polymer
9
Fig.1.6.1.2 Example on nonionic water insoluble cross-linked
superabsorbent polymer, ethylcellulose crosslinked
with epichlorohydrin
10
Fig.1.6.1.3 Examples on SAP cross-linking agents 11
Fig.1.6.1.4 Polyacrylamide cross-linked with polyacrylic acid
via attraction between opposite charges
12
Fig.1.6.1.5 Example on physical crosslink 12
Fig.1.6.1.1.1 Preparation of polyacrylamide polymer 13
Fig.1.6.1.2.1 A representative structure of PVA 14
Fig.1.6.1.3.1 A representative structure of PEO 15
Fig.1.6.2 A representative structure of starch grafted with
polyacrylic acid
16
Fig.1.6.2.1 Polymerization of superabsorbent polyacrylates 17
Fig.1.6.2.2.1 Dimerization of acrylic acid 18
Fig.1.6.2.2.2 Michael addition of acrylic acid 18
Fig.1.6.2.2.3 Hydrolysis of the Michael addition product of
acrylic acid
19
Fig.1.8 Chemical structure of the reactants and general ways
to prepare an acrylic SAP network: (a) cross-linking
polymerization by a polyvinylic cross-linker,(b)
cross-linking of a water – soluble prepolymer by a
polyfunctional cross-linker . R is aliphatic group . M
= sodium or potassium cations . X= O, NH.
23
Fig.1.9.1 The mechanism of in-situ cross-linking during the
alkaline hydrolysis of polysaccharide-g-PAN
copolymer to yield superabsorbing hybrid materials
25

XI
No. Figure Page
Fig.1.9.2.1 Typical cellulose – based SAP prepared via direct
cross-linking of sodium carboxyl methylcellulose
(CMC; R=H , COO-Na+
) or hydroxyethyl cellulose
(HEC ; R=H , CH2CH2OH)
27
Fig.1.9.2.2 Chemical structure and general ways to prepare sodium
carboxy methylcellulose
29
Fig.1.12 Sugar structure 36
Fig.2.1 Preparation of Allyl sucrose by method A 38
Fig.2.2 Preparation of Epoxy allyl sucrose by method B 41
Fig. 2.6 A typical AUL tester picture and various parts 50
Fig.2.11.2 Plate assay to visualize biodegradation of Allyl sucrose
and Epoxy sucrose by Pseudomonas aeruginosa and
Trichophytonrubrum. A-1, biodegradation of Allyl
sucrose by Pseudomonas aeruginosa; A-2,
biodegradation of Epoxy sucrose by Pseudomonas
aeruginosa; B-1, biodegradation of Allyl sucrose by
Trichophytonrubrum;B-2biodegradation of Epoxy
sucrose by Trichophytonrubrum
56
Fig.3 The chemical structure and 1
H-NMR of sucrose 58
Fig. 3.1.1
1
H-NMR of Allyl sucrose 61
Fig. 3.1.2 C-13 NMR of Allyl sucrose 62
Fig. 3.1.3
1
H-NMR of Epoxy allyl sucrose 63
Fig. 3.1.4 C-13 NMR of Epoxy allyl sucrose 64
Fig. 3.2.1 Polymerization of acrylic acid in presence of cross-
linker AS
65
Fig.3.2.2 Polymerization of acrylic acid with cross-linking agent
EAS
87
Fig.3.2.3 Polyacrylic acid cross-linked with 1,4-BDGE 68
Fig.3.2.4 Polyacrylic acid cross-linked with EGDA 69
Fig.3.3.1 IR for three of the prepared polymers 71
Fig.3.3.3 SEM micrographs of prepared SAP’s: A is for
superabsorbent polymer cross-linked with 5% AS
(PAA-AS) x1000; B is for superabsorbent polymer
cross-linked with 5% EAS (PAA-EAS) x500; B is for
superabsorbent polymer cross-linked with 5% EAS
(PAA-EAS) x1000. C is for superabsorbent polymer
cross-linked with 5% EGDA (PAA-EGDA) x1000
72
Fig.3.3.7 DSC for SAPs 81

XII
No. Figure Page
Fig. 3.4 Plate assay to visualize biodegradation of Allyl sucrose
and Epoxy sucrose by Pseudomonas aeruginosa and
Trichophytonrubrum. A-1, biodegradation of Allyl
sucrose by Pseudomonas aeruginosa; A-2,
biodegradation of Epoxy sucrose by Pseudomonas
aeruginosa; B-1, biodegradation of Allyl sucrose by
Trichophytonrubrum; B-2 biodegradation of Epoxy
sucrose byTrichophytonrubrum
83

XIII
List of Graphs
No. Graph Page
Graph 3.3.4.1 Absorbency of PAA-AS. 75
Graph 3.3.4.2 Absorbency of PAA-EAS. 76
Graph 3.3.4.3 Absorbency of PAA-EGDA. 77
Graph 3.3.4.4 Absorbency of PAA-1,4-BDGE. 78

XIV
List of Appendices
No. Appendix Page
Fig. A1 IR for AS. 96
Fig. A2 IR for EAS. 97
Fig. A3 IR for EGDA. 98
Fig. A4 IR for prepared SAPs (AS, EAS, EGDA) 99
Fig. A5 Electronic Image for prepared SAP (PAA – AS), Input
Source: Secondary electron detector, Image Width:
1.263 mm
100
Fig. A6 Electronic Image for prepared SAP (PAA – AS), Input
126.3 mm
101
Fig. A7 Electronic Image for prepared SAP (PAA – EAS), Input
1.263 mm
102
Fig. A8 Electronic Image for prepared SAP (PAA – EAS), Input
126.3 mm
103
Fig. A9 Electronic Image for prepared SAP (PAA – EGDA),
Input Source: Secondary electron detector, Image
Width: 1.263 mm
104
Fig. a10 Electronic Image for prepared SAP (PAA – EGDA),
Input Source: Secondary electron detector, Image
Width: 126.3 mm
105
Fig. a11 DSC for prepared SAP (PAA-AS) 106
Fig. a12 DSC for prepared SAP (PAA-EAS) 107
Fig. a13 DSC for prepared SAP (PAA-1,4-BDGE) 108
Fig. a14 DSC for prepared SAP (PAA-EGDA) 109
Fig. a15 DSC for prepared SAPs. (PAA-AS, EAS, 1,4-BDGE,
EGDA)
110

XV
List of abbreviations
Superabsorbent polymersSAPs
Allyl SucroseAS
Epoxy Allyl SucroseEAS
1,4-butanediol diglycidyl ether1,4-BDGE
Ethylene Glycol DiacrylateEGDA
meta Chloroperoxybenzoic acidM-CPBA
Poly Acrylic AcidPAA
Acrylic AcidAA
Starch – graft polyacrylonitrileSPAN
Polyvinyl alcoholPVA
Poly ethylene oxidePEO
Acryl amideAM
PolyacrylamidePAN
MethoxyhydroquinoneMHQ
Acrylic Acid DimerDAA
Hydroxypropionic acidHPA
MethacrylamideMAM
Methacrylic acidMAA
AcrylonitrileAN
2- HydroxyethylmethacrylateHEMA
2-acrylamido – 2- methyl propaneAPMS
N- vinyl pyrrolidoneNVP
vinyl sulphonic acidVSA
vinyl acetateVAC
Divinyl sulphoneDVS
Carbomethoxy celluloseCMC
Hydroxyethyl celluloseHEC
Monochloroacetic acidMCAA
Ethylene diamine tetraacetic dianhydrideEDTAD
Absorbency Under LoadAUL
Nutrient AgarNA
Sabouraud DextroseSDA
Trimethylolpropane triacrylateTMPTA
Thermal AnalyzersTA

XVI
By
Firas Jaber Abu Jaber
supervisor
Dr. Othman Hamed
Abstract
New Sucrose – based monomers were prepared. The prepared
monomers are Allyl Sucrose (AS) and Epoxy Ally Sucrose (EAS). Allyl
sucrose was prepared by reacting sugar with allyl chloride in an alkaline
medium. Allyl sucrose was then converted into epoxy allyl sucrose by
epoxidation with m-chloroperoxybenzoic acid (m-CPBA). The prepared
sucrose-based monomers were characterized by 1
H and 13
C NMR
spectroscopy. Both sucrose-based monomers were then used as cross-
linking agents to prepare an entirely new class of special biodegradable
superabsorbent polymers. In addition, other cross-linking agent were also
used including 1,4-butanediol diglycidyl ether (1,4-BDGE), and ethylene
glycol diacrylate (EGDA). Ethylene glycol diacrylate was chosen because
it is a well known cross-linking agent that is reported in the literature as a
cross-linking agent for superabsorbent polymers. 1,4-Butanediol diglycidyl
ether was used for the first time as cross-linking agent for superabsorbent
polymer. The absorbency for the prepared SAP’s were evaluated. Free
swell for the prepared polymers was measured using the tea bag test, and
the absorbency under load was measured using the hanging cell test

XVII
method. Results showed that the free swells and absorbency under load
decrease by increasing percentage of cross-linking agent, lowest
absorbency observed at cross-linking about 4%. SAP cross-linked with
EAS has the highest absorbent capacity and absorbency under load. This
could be because it has the highest polarity and highest number of hydroxyl
groups.
The advantages of the prepared polymers over the commercial one
are that: first; they are biodegradable as shown by the biodegradability test;
second, they are prepared in one step process. Since the commercial SAP is
prepared in a two-step process, in the first step the acrylic acid is
polymerized with the cross-linking agent then the produced SAP is surface
cross-linked to enhance it absorbency under load.

1
Chapter One
Introduction
1.1 Background
Superabsorbent polymers (SAPs) are hydrophilic networks which
have the ability to absorb and retain large amounts of fluid without
dissolving and the absorbed fluid is hardly removable even under some
pressure [1]. In water SAPs swells to a rubbery gel to their mass can absorb
and retain extraordinary large amounts of water or aqueous solution [2].
These ultrahigh absorbing materials can imbibe deionized water as high as
1000-100000% (10-1000g/g) whereas the absorption capacity of common
hydrogels is not more than 100% (1g/g). Visual and schematic illustrations
of an acrylic – based anionic superabsorbent hydrogel in the dry and water-
swollen states are given in Fig.1.1 [3].

2
Fig. 1.1: (i) A visual comparison of the SAP single particle in dry (right) and swollen state
(left). (ii) A schematic presentation of the SAP swelling [3,4].
Traditional absorbent materials such as tissue paper and
polyurethane foams unlike SAPs, will lose most of their absorbed water
when they are squeezed.

3
Table 1.1 : Comparison between the absorbing capacity of common
materials with SAP [2-5].
Absorbent Materials Water Absorbency (wt%)
Filter paper
Tissue paper
Soft polyurethane sponge
Wood pulp fluff
Cotton ball
Agricultural SAP
180
400
1050
1200
1890
20200
1.2 Superabsorbent Polymers Physical Shapes
SAPs are produced in various forms like for instance powder, fiber,
foam and film. The SAP particle shape (granula, fiber, film,….etc) has to
be basically preserved after water absorption and swelling, i.e ., the swollen
gel strength should be high enough to prevent a loosening, mushy, or slimy
state [6]. This is a major practical feature that distinguishes SAPs from
other hydrogels. Usually this is done by lightly cross-linking of SAPs to
produce a net work that can swell in water and hold large amount of fluid
while maintaining its shape. Example on crosslinked polymer is shown in
Fig.1.2.1 [7].

4
O
O
OHO
OH
HO OH
O
HO OH
O
O
OO
OH
HO O
OH
HO OH
O
O
OO
OH
HO OH
O
HO OH
O
O
OO
OH
HO OH
O
HO OH
O
O
OHO
OH
HO O
OH
O OH
O
O
OO
O
HO OH
O
HO OH
O
O
OO
OH
HO OH
OH
O OH
O
O
OO
OH
HO O
OH
O OH
O
O
OHO
O
HO OH
O
HO OH
O
O
OO
OH
HO OH
OH
HO O
O
O
OO
OH
O OH
OH
HO OH
O
O
OO
O
HO OH
OH
HO OH
O
O
OHO
OH
HO OH
OH
HO O
O
O
OO
OH
HO OH
OH
HO OH
O
O
OO
O
HO OH
OH
HO OH
O
O
OO
OH
HO OH
OH
HO OH
HOHO
HO
HO
HO
HO
HO
HO
HO
Fig.1.2.1: Cellulose polymer cross-linked with epichlorohydrin.
Examples on some of the cross-linking agent used SAP cross linking
are summarized in Fig. 1.2.2 that include ethylene glycol dimethacrylate,
TMPTA, and diethyleneglycol diacrylate are examples of cross-linkers
made by esterification of multifunctional alcohols, N,N'-
methylenebisacrylamide (MBA) and 1,4-butanediol diacrylate (BDDA),
and epichlorohydrin. These are used as the water and the oil soluble
crosslinkers, respectively [8, 9].

5
Fig. 1.2.2: Structures of some of the cross-linking agents.
1.3 Water Absorbents
Water Absorbent materials are usually categorized into two major
classes based on the mechanism of water absorption, i.e., chemical and
physical absorptions. Chemical absorbers (e.g., metal hydrides) hold water
via chemical reaction converting their entire nature. Physical absorbers
hold water via four main mechanisms; (1) reversible changes of their
crystal structure (e.g., silica gel and anhydrous inorganic salts); (2) physical
trap of water via capillary forces in their macro –porous structure (e.g., soft
polyurethane sponge); (3) a combination of the mechanism of physical trap
2 and hydration of functional groups (e.g., cellulose); (4) mechanism that
involves combination of mechanisms of 2 and 3 and essentially dissolution

6
and thermodynamically favored expansion of the macromolecular chains
limited by cross-linkages [6] .
1.4 Applications
Due to their excellent water absorbing properties, SAPs have an
unlimited number of applications. They are used as scaffolds in tissue
engineering where they may have human cells in order to repair tissue.
Superabsorbent polymers have the ability to sense environmental changes,
like as changes of pH, temperature. Hydrophilic networks that are
responsive to some molecules, such as glucose or antigens can be used as
biosensors as well as in drug systems, disposable sanitary products (for
example, diapers, incontinence articles, feminine hygiene products, airlaids
and absorbent dressings), and in controlled release drugs [10].
Superabsorbent polymers were also employed in various applications, such
as household articles, sealing materials, humectants for agricultural
products for soil conditioning, oil-drilling, anti-condensation coatings,
water-storing materials in agriculture, absorbent paper products, bandages
and surgical pads, pet litter, wound dressings, and as chemical absorbents.
Furthermore, they are used in food packaging applications [11].
1.5 History and Market
The synthesis of the first water-absorbent polymer prepared from
acrylic acid (AA) and the crosslinking agnet divinylbenzene (Fig.1.5.1),

7
were both thermally polymerized in an aqueous medium, and then the first
generation of hydrogels was appeared [12]. These hydrogels were mainly
based on hydroxyalkyl methacrylate and related monomers with swelling
capacity up to 40-50%.
CO2
-
CO2
-
CO2
-
CO2
-
CO2
-
CO2
-
CO2
-
CO2
-
CO2
-
CO2
-
CO2
-
CO2
-
CO2
-
CO2
-
CO2
-
CO2
-
CO2
-
CO2
-
CO2
-
CO2
-
Fig. 1.5.1: Superabsrobent polymer made from acrylic acid and divinylbenzene.
They were used in developing contact lences which have make a revolution
in ophthalmology, and the first commercial SAP was produced through
alkaline hydrolysis of starch–graft-polyacrylonitrile (SPAN) is shown in
Fig.1.5.2.
O
HO OH
HOH2C
O + H2C CHCN
O
HO OH
HOH2C
O (CH2CH)n
CN
Polyacrylonitrile Starch Graft Polymer
Initiator
O
HO OH
HOH2C
O (CH2CH)n
COO-
Na+
Fig.1.5.2: Superabsrobent polymer made from Starch grafted polyacrylonitrile.

8
1.6 Types of superabsorbent polymers and methods of
preparation
Superabsorbent polymers can be classified based on the basis of
presence or absence of electrical charge in the SAPs cross-linked chains
as ionic or nonionic polymers. The ionic polymers may be an anionic or
a cationic based on the charge present on the polymer chains positive or
negative [13].
1.6.1 Nonionic Polymer
Nonionic polymers absorb water and aqueous fluids by means of
the energetic and entropic interactions made possible by mixing the
aqueous fluids with the hydrophilic groups that are present along the
polymer chain. Example on this type of polymer is methylcellulose and
ethylcellulose is shown in Fig. 1.6.1.1.

9
Fig.1.6.1.1: Example on nonionic water soluble SAP.
In this class of absorbents water molecules are solvated through
hydrogen bonds. In addition, the entropy of the system may be increased
during mixing by a decrease in the partially ordered structure of pure liquid
water. These are the same phenomena that lead to the dissolution of water –
soluble polymers [14]. The principle distinction of absorbent polymers over
water-soluble polymers is the presence of crosslinks within the molecular
structure of the absorbent polymers. The crosslinks connect the various
polymer chains into a huge insoluble molecule that nevertheless can change
its shape and volume as it becomes solvated by water is shown in
Fig.1.6.1.2. The result of the absorption of solvent is a swollen, soft gel.

10
Fig.1.6.1.2: Example on nonionic water insoluble cross-linked SAP, ethylcellulose
crosslinked with epichlorohydrin.
The nature of the crosslinks plays a significant role in the properties
of superabsorbent polymers. There are three principal bonding types that
are used to bind the polymer chains together: covalent, ionic, and hydrogen
bonds. Two basic methods are used to introduce covalent crosslinks. First,
covalent crosslinks are formed when the major monomers (e.g., acrylic
acid) is copolymerized with a di-,tri-, or tetra – vinyl monomer such as
N,N-methylenebis(acrylamide), 1,1,1-trimethylolpropanetriacrylate, or
tetraallyloxyethane, in a free radical initiated addition polymerization [15].

11
Fig.1.6.1.3: Examples on SAP cross-linking agents.
Covalent cross-links are also introduced by reacting the polymer
chains with a di- or tri - functional reagents that reacts with the carboxylic
acid groups by means of a condensation or addition reaction.
Second, ionic cross-links are formed by reacting a polyvalent ion of
opposite charge with the charged polymer chains. The crosslink forms as a
result of charge association of the unlike charges as shown in Fig.1.6.1.4.
Because the bond is formed by ion association (charge neutralization) the
chemical structure of the cross-linker is less important in determining the
placement of the cross-links compared with covalent cross-links. If ionic
components are present in the liquid to be absorbed, ion exchange may
occur with the ionic cross-links, which may alter the nature of the cross-
links and the behavior of the polymer in ways that may be unforeseen. Also
because the interionic reaction is very fast.
The incorporation of the crosslink and the resulting structure of the
crosslinked polymer can be difficult to control.

12
Fig.1.6.1.4: Polyacryl amide cross-linked with polyacrylic acid via attraction between
opposite charges.
The third type of crosslink is the physical crosslink, which is usually
formed by means of hydrogen bonding of segments of one chain with the
segments of another chain is shown in Fig.1.6.1.5.
Fig.1.6.1.5: Example on physical crosslink.
A number of nonionic water-soluble polymer types are known, and
these may be used as absorbent polymers when cross-linked. Outside of the
large contribution of ions to swelling, some of the important characteristics
that should be available in polymer to be absorbent polymers are for
example, the molecular weight of the polymer chains should be large for
optimum absorbency, and the absorbency depends on the mass of the
monomer unit and its solvating character. A high-molecular weight,

13
hydrophobic monomer will not yield an absorbent polymer optimized for
water absorption on a weight basis [16].
1.6.1.1 Polyacrylamide
Polyacrylamide is a well-known water soluble polymer and has been
cross-linked by numerous methods to form an absorbent polymer [17].
Unless some of the amide functions are hydrolyzed to anionic carboxylates,
the polymer is nonionic. Acrylamide is one of the very few monomers that
can be easily polymerized to extremely high molecular weight 10 million
g/mol), which is an advantage for making absorbent polymers. Example on
acrylamide is shown in Fig.1.6.1.1.1. A major disadvantage is the practical
difficulty of removing the quantity of unpolymerized acrylamide in the
final product. This is a well documented toxicology of acrylamide
monomer [18].
Fig.1.6.1.1.1: Preparation of polyacrylamide polymer [19].

14
1.6.1.2 Polyvinyl Alcohol (PVA)
Polyvinyl alcohol gels have been used as absorbent polymer. They
are prepared by reacting vinyl acetate to form poly (vinyl acetate) followed
by hydrolyzing the poly (vinyl acetate) to poly (vinyl alcohol) as shown in
Fig.1.6.1.2.1, and finally reacting with a crosslinker such as a
polycarboxylic acid (forming ester crosslinks). Poly (vinyl alcohol) is
limited to practical molecular weight of about 700,000 g/mol as a result
significant chain transfer reactions to the monomer and can be highly
crystalline; both features limit the swelling properties of PVA. The
monomer is moderately expensive when compared to acrylamide [20].
Fig.1.6.1.2.1: A representative structure of PVA.
1.6.1.3 Polyethylene Oxide (PEO).
Polyethylene oxide has rarely been used as an absorbent polymer,
even though the monomer has relatively lower price. The polymer is
usually prepared from polymerizing of ethylene oxide shown in
Fig.1.6.1.3.1. The molecular weight of the polyoxide is limited to about
600,000 g/mol. Cross-linking may occur either by end linking the hydroxyl

15
end groups with an appropriate reagents such as for example
polyisocyanates or by means of radiation treatment. Efficient end linking is
quite difficult for very high molecular weight polymers as a consequence of
the low concentration of end groups. Poly (ethylene oxide) is known to be
highly crystalline, which makes its water absorbency decrease [21,22].
Fig.1.6.1.3.1: A representative structure of PEO
1.6.2 Natural Polymer
Natural polymer are divided into two main groups: polysaccharides
and polypeptides (proteins). SAPs are prepared from natural polymer
through addition of some synthetic parts onto the natural substrates, e.g.,
graft copolymerization of vinyl monomers on polysaccharides. Example
on this type of polymer is shown in Fig.1.6.2. In this figure a structure of
starch grafted with polyacrylic acid is shown.

16
O
HO OH
HOH2C
O + H2C CHCOO-
O
HO O
HOH2C
O
Polyacrylic acid Starch Graft Polymer
Initiator
n
Ce(II)
n
CO2
-
CO2
-
CO2
-
CO2
-
CO2
-
Fig.1.6.2: A representative structure of starch grafted with PAA.
SAPs are also classified based on the type of monomeric unit in their
chemical structure, thus the most traditional SAPs fall in one of the
following categories: [23]
1. Cross-linked polyacrylates and polyacrylamides.
2. Hydrolyzed cellulose-polyacrylonitrile (PAN) or starch –PAN
graft copolymers.
3. Cross- linked copolymers of maleic anhydride.
1.6.2.1 Anionic Superabsorbent Polymers
The most conventional type of anionic SAPs is the acrylic polymer
that comprises a copolymeric net-work based on the partially neutralized
acrylic acid (AA) or Acrylamide (AM); As shown in Fig.1.6.2.1.
Polyacrylic polymer has partial neutralization products of polymerized

17
acrylic acid monomer, its salts, and acrylamide via solution or inverse-
suspension polymerization techniques such as starch-acrylonitrile and
starch –acrylic acid graft copolymers and polyacrylic acids.
Fig.1.6.2.1: Polymerization of Superabsorbent Polyacrylates.
The materials biodegradability is a main focus in this research
because of the rebuilt concern towards environmental protection issues.
The half life is in general in the range 5-7 years, and they decompose into
carbon dioxide, ammonium, and water [24].
1.6.2.2 Monomers for Acrylic Anionic Polymers
Acrylic acid (AA) and its sodium or potassium salts, and acrylamide
(AM) are most often used in the industrial production of SAPs.
The AA monomer is unstable dimerize or trimerizes at room
temperature in presence of air to form dimer as shown in Fig.1.6.2.2.1. This
process is usually inhibited by free radical scavenger
methoxyhydroquinone (MHQ). In industrial production, the inhibitor is not

18
usually removed due to some technical reasons [25]. Meanwhile, AA is
converted to an undesired dimer that must be removed or minimized.
Fig.1.6.2.2.1: Dimerization of acrylic acid.
The minimization of acrylic acid dimer (DAA) in the monomer is
important due to its indirect adverse effects on the final product. As soon as
AA is produced, diacrylic acid β-acryloxypropionic acid) is formed
spontaneously in the bulk of AA via a sluggish Michael-addition reaction
as shown in Fig.1.6.2.2.2 [26].
Fig 1.6.2.2.2: Michael addition of acrylic acid.
Since temperature, water content, and pH have impact on the rate of
DAA formation, the rate can be minimized by controlling the temperature
of stored monomer and excluding the moisture. Increasing water
concentration has a relatively small impact on the DAA formation rate. The
rate of dimerization roughly doubles for every 5 C˚ increase in temperature.

19
For example, in an AA sample having 0.5% water, the dimerization rate is
76 and 1672 ppm/day at 20 C˚ and 40 C˚, respectively. DAA, however, can
be hydrolyzed in alkaline media as shown in Fig.1.6.2.2.3 to produce AA
and β-hydroxypropionic acid (HPA). Since the latter is unable to be
polymerized, it remains as part of the SAP soluble fraction. Fortunately,
alkaline media used conventionally for AA neutralization with NaOH
favors this hydrolytic reaction. For instance, in an 80% neutralized AA, the
dimerization rate at 23 C˚ and 40 C˚ has been determined to be 125 and 770
ppm/day, respectively [27].
DAA can also be polymerized to go into the SAP network by using
strong base or by heating in the drying step of the final product. As a
result, free AA will be released and causes the enhancement of the level of
residual monomer as shown in Fig1.6.2.2.3 [2,28].
Fig.1.6.2.2.3: Hydrolysis of the Michael addition product of acrylic acid.

20
1.7 Preparation of Superabsorbent Polyacrylates
Superabsorbent polyacrylates are prepared by free-radical initiated
polymerization of acrylic acid and its salts with a cross-linker in aqueous
solution or as a suspension of drops of aqueous solution in a hydrocarbon.
The polymerization is shown in Fig1.6.2.1. The two principle processes,
bulk solution polymerization and suspension polymerization share many
features. The monomer and crosslinker concentration, the initiator type
and concentration, polymerization modifiers, the relative reactivities of the
monomer, the basic polymerization kinetics, and the reaction temperature
are all significant factors in both processes [29].
In either process, the monomer is dissolved in water at concentration
of 20-40 wt%, and the polymerization is initiated by free radicals in the
aqueous phase. Several types of free-radical sources may be used,
including thermally decomposable initiator, redox systems, photochemical
initiator, and combinations of them
The monomers are polymerized either in the acid form (pH 2- 5) or
as the partially neutralized salt ( pH 5-7). Inexpensive bases, such as
sodium hydroxide and sodium carbonate are used as neutralizing agents. A
choice would be made based on consideration of the pH of the base
solution and the resulting potential for hydrolyzing the cross-linker, the
solubility limits of the base in water and on the solubility of the monomer
salt in water. In suspension polymerization, the acrylic acid must be

21
neutralized prior to polymerization because of a substantial partition
coefficient of acrylic acid in the liquid hydrocarbons used as continuous
phase [30].
The polymers made from acrylic acid (and neutralized later) or from
the partially neutralized monomer are somewhat different because of the
presence or absence of charged monomers and polymers during the
formation of the polymer network.
Small amounts of cross-linker play a major role in modifying the
properties of superabsorbent polymers. The co-polymerizable cross-linkers
used in superabsorbent polymers range from di-functional compounds
mentioned earlier in this chapter [31].
In addition to modifying the swelling and mechanical properties, the
cross-linker affects the amount of soluble polymer formed during the
polymerization as a result of its relative reactivity with acrylic acid or
sodium acrylate. Efficiency of cross-linking will also depend on steric
hindrance and reduced mobility at the site of pendant double bonds, the
tendency of a given cross-linker to undergo intermolecular addition
reactions (cyclopolymerization), and the solubility of the cross-linker in the
monomer mixture [32].
Other monomers that are used to make anionic SAP include
monomers such as methacrylic acid (MAA), methacrylamide (MAM),
acrylonitrile (AN), 2-hydroxyethylmethacrylate (HEMA), 2-acrylamido-2-

22
methylpropane sulphonic acid (APMS), N-vinylpyrrolidone (NVP), vinyl
sulphonic acid (VSA) and vinyl acetate (VAC).
Major disadvantage about these synthetic polymers is poor in
degradability, and then there remains an environmental problem with
superabsorbent polymers [33].
1.8 Superabsorbent Polymers Origins
The greatest volume of SAPs comprises full synthetic or of
petrochemical origin. They are produced from the acrylic monomers,
mostly made up from acrylic acid (AA), its salts and acrylamide (AM).
(Fig.1.8) shows two ways to prepare acrylic SAP networks, i.e.,
simultaneous polymerization and crosslinking by a polyvinylic cross-
linker, and cross-linking of a water–soluble prepolymer by a polyfunctional
cross-linker [33].

23
Fig.1.8: Chemical structure of the reactants and general ways to prepare an acrylic SAP
network: (a) cross-linking polymerization by a polyvinylic cross-linker, (b) cross-linking of
water – soluble prepolymer by a polyfunctional cross-linker. R is aliphatic group. M = sodium
or potassium cations. X= O, NH [33].
1.9 Polysaccharide-Based Superabsorbent Polymers
Polysaccharides are polymers of monosaccharides, which are
cellulose, starch, and natural gums (such as xanthan, guar, and alginates)
are some of the most important polysaccharides.
Preparing polysaccharide-based SAPs fall under two main groups;
(a) graft copolymerization of vinyl monomer(s) on polysaccharide in the
presence of cross-linker, and (b) direct cross-linking of polysaccharide
[34].

24
1.9.1 Preparation of SAP Based Polysaccharides by Graft
Polymerization
In graft co-polymerization, a polysaccharide is reacted with vinyl
monomers in presence of an initiator by two separate ways. First, the
neighboring OHs on the saccharide units and the initiator interact to form
redox pair-based complexes. These complexes are dissociated to form
carbon radicals on the polysaccharide substrate via homogeneous cleavage
of the saccharide C-C bonds. The free radicals initiate the graft
polymerization of the vinyl monomers and cross-linker on the substrate.
The second way for initiation, an initiator such as persulphate
(Na2S2O8) may abstract hydrogen radicals from the OHs of the
polysaccharide to produce the initiating radicals on the polysaccharide
backbone [35].
The earliest commercial SAPs were produced from starch and
acrylonitrile (AN) monomer by the first mentioned method without
employing a cross-linker. The starch g-PAN copolymer (SPAN) was then
treated in alkaline medium to produce a hydrolyzed SAP (HSPAN) while
an in-situ cross-linking occurred simultaneously. This approach is
summarized in Fig.1.9.1.

25
Fig.1.9.1: The mechanism of in-situ cross-linking during the alkaline hydrolysis of
polysaccharide-g-PAN copolymer to yield superabsorbing hybrid materials [33].
In the method direct cross-linking of polysaccharide, polyvinylic
compounds (e.g., divinyl sulphone, DVS) or polyfunctional compounds
(e.g., glycerol, epichlorohydrin and glyoxal) are often employed, POCl3 is
also used for the cross-linking [18].
1.9.2 Preparation of SAP Based Polysaccharides by Cross-linking
Polysaccharide based polymer such as carboxymethyl cellulose
(CMC) is crosslinked with polyacids to form crosslinked polymer via ester
covalent bonds. Sodium carboxymethyl cellulose is a semisynthetic
polymer made by reacting chloroacetic acid with sodium cellulose in slurry
with isopropanol and water. Sodium cellulose is made by swelling highly
crystalline cellulose with an aqueous solution of sodium hydroxide to
decrystallize the cellulose and allow homogeneous penetration of the
chloroacetic acid. The rigidity of the cyclic cellulose backbone polymer
provides for good superabsorbency when the soluble Sodium
carboxymethyl cellulose is crosslinked.

26
Crosslinked Sodium carboxymethyl cellulose has several
disadvantages, however. The molecular weight of cellulose that is isolated
in a pulping process from tree fiber is low (350,000 g/mol) compared with
some of the synthetic polymers, but, at additional cost, cotton linters can
provide cellulose with higher molecular weight (1.2 million g/mol)
necessary for improved absorbency [17].
Preparing a superabsorbent from Sodium carboxymethyl cellulose
also requires crosslinking of a viscous polymer solution, which adds to the
cost of this material. In addition, crosslinking Sodium carboxymethyl
cellulose is inefficient with typical crosslinkers like divinyl sulfone or
glyoxal, because the most reactive hydroxyl groups of cellulose have been
substituted with carboxyl groups [36].
As shown in Fig.1.9.2.1 the crosslinked of CMC-and hydroxyethyl
cellulose (HEC) – based SAPs with diethylsulfone was prepared by
Saninno et al converted into natural SAP hydrogels via cross-linking with
citric acid [37].

27
Fig.1.9.2.1: Typical cellulose – based SAP prepared via direct cross-linking of sodium
carboxylmethyl cellulose (CMC; R=H, COO-
Na+
) or hydroxyethyl cellulose (HEC; R=H,
CH2CH2OH) [36].
Sodium carboxymethyl cellulose belongs to the the class of ionic
polymers that are based on naturally occurring polysaccharides. Sodium
carboxymethyl cellulose is used in detergents, mining and oil industry, the
cosmetics and personal hygiene industries, the paper industry, and food
industry. It is prepared as shown in Fig1.9.2.2 by dissolving cellulose in
50% sodium hydroxide solution, slurrying the mixture in isopropanol , and
reacting with monochloroacetic acid (MCAA). The product is neutralized
with hydrochloric acid and dried [38].
Other ionic polysaccharides include the sodium alginate,
carrageenans (from seaweeds), pectins (from plant extracts), and xanthan

28
(from microbial fermentation process). These polymers also become
superabsorbent when crosslinked.
Another example on anionic SAP based natural polymer is sodium
alginate which is a polysaccharide produced by brown seaweeds such as
the giant kelp and isolated by extraction and precipitation of the
polysaccharide from the seaweed. The molecular weight of the product is
about 250,000 g/mol. The polymer is relatively expensive as a result of the
harvesting and extraction processes used in its isolation [39].
A number of cationic polymers are also known and can function as
superabsorbent when crosslinked, including poly
(diallyldimethylammonium chloride), poly(vinyl pyridine),
poly(vinylbenzyltrimethylammonium salts), cationic starches, and
hydrolyzed chitin (chitosan ), which is derived from the exoskeletons of
arthropods such as lobster. A cationic monomer is co-polymerized with a
less expensive nonionic monomer such as acrylamide to make the cationic
polymer. In general, a combination of complex processing conditions and
relatively low molecular weight leads to higher cost and lower
effectiveness of the cationic polymers compared with the anionic polymers
[40].

29
Fig.1.9.2.2:Chemical structure and general ways to prepare Sodium carboxymethyl cellulose.
1.10 Polyamino Acid - Based Superabsorbent Polymers
Proteins from soybean, fish, and collagen – based proteins are the
most frequently used hetero-polypeptides for preparation of super –
swelling hydrogels.
Soy and fish proteins are converted into SAP by a two period
process, in the first stage protein react with Ethylenediaminetetraacetic
Dianhydride (EDTAD). EDTAD has low toxicity. In the second stage, the
remaining amino groups of the hydrophilized protein are lightly cross-
linked by glutaraldehyde to yield a hydrogel network with superabsorbing
properties. The SAP was capable of absorbing and retaining 100-350 g of
water/g of dry gel after centrifugating it holds about 214 g /g hydrogel,
depending on the extent of protein structure, cross-link density, and
environmental conditions such as pH, ionic strength, and temperature [41].
On the other hand proteins are modified by polysaccharides or
synthetics to produce hydrogels with super-swelling properties, modified
proteins with some water-soluble, hydrophilic, biodegradable, and non-

30
toxic polymers, e.g., sodium carboxymethyl cellulose, poly(ethelene
glycol), poly(vinyl alcohol), chitosan [42].
Collagen –based proteins including gelatin and hydrolyzed collagen
(H-collagen) have been used for preparing SAP materials, e.g., gelatin-g-
poly(NaAA-co-AM) hydrogel has been synthesized through simultaneous
cross-linking and graft polymerization of AA / AM mixtures onto gelatin
H-collagen was also graft copolymerized with AA, binary mixtures of AA
and AM, AM and methacrylic acid (MAA) for preparation of SAP hybrid
materials.
Homo-poly(amino acid) of poly(aspartic acid), poly(L-lysine) and
poly γ-glutamic acid ) have also been employed to prepare SAP materials,
super – swelling hydrogels on poly γ-glutamic acid), PGA, has been
prepared by cross-linking reactions via both irradiation and chemical
approaches. Similar to PGA, highly swollen hydrogels based on L-lysine
homopolymer have been also prepared simply by γ-irradiation of their
aqueous solutions [43].
1.11 Importance of Biodegradable Superabsorbent Polymers
Because about 90% of all superabsorbent materials are used in
disposal articles, most of which are disposed of in landfills or by
incineration, there is a perceived environmental problem with
superabsorbant polymers, life cycle analyses of both disposable and cloth

31
diapers manufactured have shown that there is no clearly superior choice in
terms of environmental impact [44].
Disposable diapers have been modified to use fewer raw materials,
which should result in a reduced solid waste burden, reduced packaging
cost, and reduced transportation costs. Despite the technical analysis,
consumer clearly perceives disposable absorbent products, specifically
diapers, as having a negative impact on the environment. Therefore,
superabsorbent polymer producers have been interested in developing
biodegradable superabsorbent polymers to serve as a component in a fully
biodegradable diaper or other absorbent product [45].
Articles incorporating biodegradable superabsorbents might be
disposed of in municipal composting facilities or flushed down to the toilet
to degrade in domestic septic tanks or at municipal waste water plant.
Several diapers claiming biodegradability have been marketed, but none
has enjoyed commercial success. It should be emphasized that the
superabsorbent polymer is only one component of a disposable absorbent
article. Significant challenges in the developments of biodegradable
alternative to other components in the absorbants article, such as water-
impermeable back sheet and adhesive tape, remain to be solved [46].
Some of the issues pertinent to biodegradable superabsorbent
polymers are also relevant to low molecular weight water soluble
polymers, therefor, new developments of biodegradable detergents builders

32
and soil anti - redeposition agents may have implication for biodegradable
superabsorbent polymer [47].
1.12 Bio-Degradability Versus Chemical Structure
The world creates billions of pounds of petroleum based waste
materials per year.
A substantial portion of the waste is discarded packaging materials
and water-absorbent materials such as disposable diapers and hygienic
products. Unfortunately, this waste is substantially non-biodegradable; in
fact, it takes approximately 450 years to degrade into polyethylene, a major
constituent of plastic waste [48].
Accordingly, environmentally unsound and potentially hazardous
methods of disposing this waste are utilized, as for example, by landfill or
incineration. Furthermore, non-biodegradable plastic is often used in
garbage bags, which in addition to creating a waste problem in of
themselves, are impermeable to most bacterial agents thereby preventing
microbial degradation of the contents within and, thus compounding the
problem of waste disposal. These problems have led the health and
environmental agencies in the world leader countries to have recently
increased interest in products made of "biodegradable" materials.
Accordingly, this have initiated research all over the world for making
biodegradable materials based on natural products such as starch, cellulose,
sugars and others [49].

33
Biodegradable describe a polymer that can be reduced to carbon
dioxide, methane, water, and biomass under biochemical action.
Biodegradability may be contrasted with the more generic term degradable.
A degradable polymer undergoes decomposition or degradation
under unspecified environmental influences. The final products of a
degradable polymer are unspecified; while a biodegradable polymer
degrades ultimately to carbon dioxide, methane and water (mineralizes)
there are several useful reviews on biodegradable water soluble polymers.
Some of the generalization that has been made about biodegradability to
chemical structure includes:
1. Naturally produced polymers biodegrade, and Chemical modified natural
polymers may biodegrade, depending on the extent of modification.
2. Synthetic addition polymers with carbon- carbon backbone do not
biodegrade at molecular weights greater than about 500g/mol.
3. Synthetic addition polymer with heteroatom in their backbone
may biodegrade.
4. Synthetic step-growth or condensation polymers are generally
biodegradable to a greater or lesser extent, depending on the chemical
nature of the chain coupling, molecular weight, morphology and
hydrophilicity [50].
5. Water solubility does not guarantee biodegradability.

34
Based on these generalities three approaches to achieving truly
biodegradable bioabsorbents materials are apparent: modification of a
superabsorbant to enhance its biodegradability or modification of a
biodegradable polymer (e.g natural polymer) to enhance its
superabsorbency [51].
The first approach would entail incorporating some biochemical
cross-linker that degrades to form smaller chain polymers. The second
approach would involve incorporating charged functional group into a
hydrophilic biopolymer to enhance its absorbency, then crosslinking the
polymer to achieve desired absorbance properties. These modifications
may impact the biodegradability of the polymer [52].
The third approach of mixing biodegradable fillers with
nonbiodegradable superabsorbance has also been attempted; however
these approaches has not led to a fully biodegradable product.
In this research we are concerned with making biodegradable sugar
based polymers using approach, and thereafter biodegradable commercial
products. The reason behind choosing sugar as the starting material in this
proposal is that, sugar is most abundant pure natural organic chemical in
the world and available at low cost [53].
The potential value of sucrose as a raw material has been recognized
for many years and has been the subject of considerable research. Although
relatively few successful derivatives of sucrose have been commercialized,

35
there has been substantial interest in developing sugar-based synthetic
technology. Sucrose is a particularly appropriate material for use in the
formation of specialty polymers and monomers produced currently from
petroleum-based materials since it is:
(a) naturally occurring and relatively inexpensive material;
(b) it is polyfunctional with three reactive primary alcohols that can
readily be derivatized (Fig.1.12) ;
(c) it is a non-reducing sugar and thus does not have the potential for the
wide variety of side-reactions that reducing sugars have and
(d) it has a relatively easily hydrolyzed glycosidic linkage that allow
sucrose polymers to be potentially more biodegradable than polymers
made with other carbohydrates [52].
Sugar-based polymers are not entirely new. For example, the
principal investigator was involved in synthesis, characterization, and
applications of sucrose-based epoxy materials developed at USDA
laboratories (New Orleans, LA, USA). It has been shown that: a) sucrose
can be converted into epoxy in two steps process in over 85% overall yield
using commercial available reagents and solvents that could be recycled at
low cost; and b) the developed epoxy material is useful in creating new
class of superabsorbent polymer [53].

36
Fig.1.12: Sugar structure.
As shown in Fig.1.12, sucrose consists of two monosaccharides,
namely glucose (C-1 to C-6) and fructose (C-1' to C-6'), positions 1', 6, and
6' contain primary hydroxyl group, where the rest of hydroxyl groups are
secondary.

37
Chapter Two
Experimental
All chemicals were purchased from Aldrich Chemical Company and
used without any further purification unless otherwise stated. All new
compounds were characterized by 1
H-NMR, 13
C-NMR, and IR
spectroscopy. Nuclear Magnetic Resonance spectra were recorded on
Varian Gemini 2000,300 MHz instrument.
All 1
H-NMR experiments are reported in δ units, ppm) downfield
from tetramethylsilane (TMS). All 13
C-NMR spectra are reported in ppm
relative to the signal of the deuterchloroform (77.0 ppm). Infrared spectra
were recorded on Perkin Elmer Model 1310 Infrared spectrometer.
Purification of samples was performed by flash chromatography on
silica gel (100-200) mesh.
2.1 Preparation of Allyl Sucrose (AS.)
Method A
In this method a solution of sucrose (10 g, 29.0 mmol in 50 mL
solvent) in N,N-dimethylacetamide (DMAc) was first prepared by stirring a
mixture of sugar in DMAc at about 60 Co
under an inert atmosphere of dry
N2 in a round bottom flask, then the solution was transferred to an
additional flask and added dropwise to a funnel that contain a suspension of
DMAc and sodium hydride (60% in oil, 20.0 g, 415 mmol, washed four

38
times with 15 mL of dry hexane) at 10 Co
over a period of 30 minutes. The
procedure was performed under an inert atmosphere of N2 to the produced
sodium sucrate mixture at 10 C°. Allyl chloride (25.0 mL added over 30
minutes) was added. After the addition was complete, the temperature
equilibrated to about 50 C°, and the contents stirred for about 90 minutes.
Later the contents were cooled to about 10 C°, quenched with 5% aqueous
sodium hydroxide (50 mL), diluted with water (500 mL) and extracted with
ethyl acetate (3×100 mL). The organic extracts were combined, washed
sequentially with water and brine (3×150 mL each), dried over anhydrous
sodium sulfate, filtered through charcoal and then concentrated in vacuum
to provide the desired products (18.0 mmol, 11.9 g) in 62% yields. The
reaction is represented in Fig.2.1.
Fig. 2.1: Preparation of Allyl sucrose by method A.

39
Method B
In this method, sucrose (100 g, 0.29 mol, 2.33 mol hydroxyl groups)
and aqueous NaOH (140.2 g in 140 mL water, 3.5 mol, 1.5 eq. /hydroxyl
group) were added to a Parr pressure vessel. The vessel was sealed, heated
with stirring to about 80 C° over 30 minutes, and maintained at that
temperature for about one hour to dissolve the reagents. The contents were
then cooled to about 60 C°, the vessel opened, and charged with cold allyl
chloride (300 mL, 3.5 mol, 1.5 equiv./hydroxyl group) in one portion. The
reactor was then sealed and pressurized with nitrogen gas (50 PSI). The
internal temperature was equilibrated to about 100 C° over a period of two
hours, and the contents were stirred overnight. Subsequently, the vessel
was cooled to room temperature, placed in an ice bath, depressurized,
opened, and diluted with ice water (500 mL) to dissolve the salts. The
contents were transferred to a separatory funnel and the mixture was
extracted with ethyl acetate (3 × 150 mL). The combined organic layers
were then washed serially with water (1 × 200 mL) and brine (1 × 200 mL),
dried over sodium sulfate, filtered, and concentrated in vacuo (40-50 C°).
Allyl sucrose C36H54O19, 178.7 g, 0.27 mol) was obtained in 80.3% yield.
The average degree of allyl substitution was 6.0 (DS=6.0, by NMR).
1
H-NMR for allyl sucrose (CDCl3) δ ppm): 3.26-4.28 sucrose[s]
hydrogens; 5.23 Ha of the glucopyranosyl moieties; 5.24 (geminal
terminal olefin hydrogens, Hb), 5.89 internal olefin Hc.). 13
C-NMR of allyl
sucrose (CDC3) δ ppm): 68.23-88.70; 104.13-104.44 (C-3 resonances of

40
the fructofuranosyl moieties of allyl sucrose); 118 (CH2-1 vinyl), 135.21
(CH2-2 vinyl).
2.2 Preparation of Epoxy Allyl Sucrose (EAS)
Method A
To a mechanically stirred solution of allyl sucrose (10 g ), urea (120
g), sodium bicarbonate (0.6 g), and manganese sulfate (0.02 g) in 20 ml
water and 110 ml of dichloromethane at 25 C° was added dropwise over a
period of four hours 20 ml of 30% of these an aqueous hydrogen peroxide.
After four hours, the reaction mixture was extracted with (4 x 50) ml
diethyl ether. The combined organic layer was dried over anhydrous
sodium sulfate, and evaporated to provide the desired product in 20% yield.
Method B
A three-neck round bottomed flask, fitted with a high torque
overhead mechanical stirrer, pressure-equalized addition funnel, and a
condenser connected to a nitrogen gas line, was placed in an ice water bath.
The flask was charged with allyl sucrose (average molecular weight 660 g,
15 mmol, 91 mmol double bonds) dissolved in ethyl acetate (50 mL), and
sodium acetate (1 g, 10% of the number of moles of m-chlororperoxy
benzoic acid) was then added to the solution. The contents were cooled to
about 5 C°, and m-chlororperoxy benzoic acid (30% in ethyl acate, 110
mol) was added dropwise into the mixture over about two hours. The

41
temperature was then raised to about 10 C°, and the contents stirred
overnight. Subsequently, the mixture was diluted with ethyl acetate (200
mL), transferred to a separatory funnel, and washed serially with cold water
(2×50 mL), cold aqueous saturated sodium carbonate (1×50 mL), and brine
(2×50 mL). The organic layer was then separated, dried over anhydrous
sodium sulfate, filtered, and concentrated in vacuo (at 50 C°) to yield EAS
as an oil that is clear and light yellow in appearance in 93% yield (9.24 g,
11.7 mmol.). No further purification was needed. The synthesis of epoxy
allyl sucrose is shown schematically in Fig. 2.2.
O
O
O O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O O
O
O
O
O
O
O
O
C36H54O11
Mol. Wt.: 662.81
MCPBA
EtOAc
5 o
C
C36H54O19
Mol. Wt.: 790.8
Fig. 2.2: Preparation of Epoxy allyl sucrose by method B.
The 1
H-NMR for epoxy allyl sucrose (EAS) (CDCl3): 2.67 (H-c,
geminal methylene of the epoxy group) 3.0-4.3 (sucrose protons and
methylenes), 4.82-4.98 (residual geminal terminal olefin hydrogens), 5.55
(H-1 signal of the glucopyranosyl moieties of the epoxy methallyl sucrose
isomers).

42
13
C-NMR for epoxy allyl sucrose (CDCl3) δ ppm): 19.24 residual
allylic CH3-d,), 51.5 (terminal epoxy allyl carbon CH2-c′), 56.1 internal
epoxy allyl carbon C-b′) 66 to 86 sucroses carbons and methylenes CH2),
89.6 (C-1 resonances of the glucopyranosyl moieties of the epoxy allyl
sucrose), 104.2 (C-2′ resonances of the fructofuranosyl moieties of epoxy
allyl sucrose isomers) and 105 (C-2′ residual resonances of the
fructofuranosyl moieties of unepoxidized methallyl sucrose isomers), 111.7
(residual CH2-c), 141.3 (residual tetrasubstituted olefin carbons C-b).
2.3 Preparation of Superabsorbent Polymer
Method A:
In this method neutralization of prepared SAP was performed after
polymerization.
2.3.1 Superabsorbent Polymer cross-linked with Allyl Sucrose (PAA-
AS.)
To a two neck round- bottomed flask under an inert atmosphere (N2)
fitted with a condenser equipped with an magnetic stirrer, allyl sucrose (1,
0.5, 0.37, 0.25, 0.06 g ) and 25 ml acrylic acid were added and the reaction
mixture was stirred for 10 minutes. Then the K2S2O8 (1 mL, 10%) was
added into the flask to initiate the reaction. First, the reaction was heated at
low temperature (about 60 Co
) once the exothermic reaction started, the
heat was turned off and reaction continued for about two hours. Gelation

43
was observed after about 40 minutes. After two hours, the produced mass
was treated with 1M sodium carbonate (40 ml) for partially neutralization.
The produced solid gel dried for 24 hours at about 80 Co
. The dried solid
was then grinded for further evaluation.
2.3.2 Superabsorbent Polymer cross-linked with Epoxy Allyl Sucrose
(PAA-EAS.)
Procedure reported in section 2.3.1 was repeated exactly except that;
ally sucrose was replaced with epoxy ally sucrose.
2.3.3 Superabsorbent Polymer cross-linked with 1,4-Butanediol
Diglycidyl Ether (PAA-1,4-BDGE.)
ally sucrose was replaced with 1, 4-butanediol diglycidyl ether.
2.3.4 Superabsorbent Polymer cross-linked with Ethylene Glycol
Diacrylate (PAA-EGDA.)
ally sucrose was replaced with ethylene glycol diacrylate.

44
2.4 Preparation of Superabsorbent Polymer
Method B:
In this method, acrylic monomer was first neutralized to a pH of
about 6.0, then polymerization performed on neutralized acrylic acid.
2.4.1 Superabsorbent Polymer cross-linked with Allyl Sucrose
Acrylic acid ( 25 ml ) was dissolved in 20 ml distilled water and then
neutralized with 37.5 ml of sodium hydroxide solution ( 8.3 M ) to pH 6.
Then acrylic acid transferred into a two neck round- bottomed flask fitted
with a condenser equipped with a magnetic stirrer and placed under an inert
atmosphere (N2). To the previous preparation, the cross-linking agent allyl
sucrose was added by (1, 0.5, 0.37, 0.25, 0.06 g) respectively, followed by
the addition of K2S2O8 (1 mL, 10%). The reaction flask with its contents
was placed in a water bath at about 40 Co
and stirred until an exothermic
reaction has started. Then the water bath was removed and the reaction
continued on its own for about two hours. The produced solid mass was
dried for 24 hours at about 80 Co
. The dried solid was then grinded for
further evaluation.
2.4.2. Superabsorbent Polymer cross-linked with Epoxy Allyl Sucrose
ally sucrose was replaced with epoxy ally sucrose.

45
2.4.3 Superabsorbent Polymer cross-linked with 1,4-Butanediol
Diglycidyl ether
ally sucrose was replaced with 1,4-butanediol diglycidyl ether.
2.4.4 Superabsorbent Polymer cross-linked with Ethylene Glycol
Diacrylate
ally sucrose was replaced with ethylene glycol diacrylate.
2.5 Tea- bag Method
SAP (0.1000 g) sample (W0) was placed into a pre-weighed tea bag
and stabled. The bag was dipped in an excess amount of water or saline
(0.9 %) solution for one hour to reach the equilibrium swelling. Then
excess solution was removed by hanging bag until no liquid was dropped
off. The tea bag was weighed (W1) and the swelling capacity was
calculated by equation (1).

46
2.5.1Tea bag test in water
Table 2.5.1.1: Free swell results of SAP cross-linked with Allyl sucrose.
AS. cross-linking
agent (%)
Weight of SAP
sample (g)
Weight of
swelled SAP (g)
Swelling capacity
g liquid/g SAP
4.0
2.0
1.5
1.0
0.5
0.1000
0.1000
0.1000
0.1000
0.1000
3.399
3.481
3.883
4.392
4.464
32.99
33.81
37.83
42.92
43.64
Table 2.5.1.2: Free swell results of SAP cross-linked with Epoxy allyl
sucrose.
EAS. cross-linking
agent (%)
Weight of SAP
sample (g)
Weight of
swelled SAP (g)
Swelling capacity
g liquid/g SAP
4.0
2.0
1.5
1.0
0.5
0.1000
0.1000
0.1000
0.1000
0.1000
3.612
4.205
4.467
4.850
4.854
35.12
41.05
43.67
47.50
47.54
Table 2.5.1.3: Free swell results of SAP cross-linked with 1,4-
Butanediol diglycidyl ether.
1,4-BDGE.
cross-linking agent (%)
Weight of SAP
sample (g)
Weight of
swelled SAP (g)
Swelling capacity
G liquid/g SAP
4.0
2.0
1.5
1.0
0.5
0.1000
0.1000
0.1000
0.1000
0.1000
3.370
3.416
3.642
3.875
3.625
32.70
33.16
35.42
37.75
35.25

47
Table 2.5.1.4: Free swell results of SAP cross-linked with Ethylene
glycol diacrylate.
EGDA.
cross-linking agent (%)
Weight of SAP
sample (g)
Weight of
swelled SAP (g)
Swelling capacity
g liquid/g SAP
4.0
2.0
1.5
1.0
0.5
0.1000
0.1000
0.1000
0.1000
0.1000
3.380
3.448
3.663
4.262
4.242
32.80
33.48
35.63
41.62
41.42
2.5.2 Tea bag test in saline solution ( 0.9 %)
Table 2.5.2.1: Free swell results of SAP cross-linked with Allyl sucrose.
AS. Cross-linking
agent (%)
Weight of SAP
sample (g)
Weight of swelled
SAP (g)
Swelling capacity
g liquid/g SAP
4.0
2.0
1.5
1.0
0.5
0.1000
0.1000
0.1000
0.1000
0.1000
2.606
2.650
2.723
2.739
2.808
25.06
25.50
26.23
26.39
27.08

48
Table 2.5.2.2: Free swell results of SAP cross-linked with Epoxy allyl
sucrose.
EAS. cross-linking
agent (%)
Weight of SAP
sample (g)
Weight of
swelled SAP (g)
Swelling capacity
g liquid/g SAP
4.0
2.0
1.5
1.0
0.5
0.1000
0.1000
0.1000
0.1000
0.1000
2.792
3.047
3.045
3.090
3.080
26.92
29.47
29.45
29.90
29.80
Table 2.5.2.3: Free swell results of SAP cross-linked with 1,4-
Butanediol diglycidyl ether.
1,4-BDGE cross-
linking agent (%)
Weight of SAP
sample (g)
Weight of swelled
SAP (g)
Swelling capacity
g liquid/g SAP
4.0
2.0
1.5
1.0
0.5
0.1000
0.1000
0.1000
0.1000
0.1000
2.517
2.315
2.589
2.605
2.777
24.17
22.15
24.89
25.05
26.77

49
Table2.5.2.4: Free swell results of SAP cross-linked with Ethylene
glycol diacrylate.
EGDA. cross-linking
agent (%)
Weight of SAP
sample (g)
Weight of
swelled SAP (g)
Swelling capacity
g liquid/g SAP
4.0
2.0
1.5
1.0
0.5
0.1000
0.1000
0.1000
0.1000
0.1000
2.485
2.407
2.640
2.643
2.837
23.85
23.07
25.40
25.43
27.37
2.6 Absorbency Under Load (AUL)
Dried SAP sample (0.1 g) was placed on the surface of gauze located
on the sintered glass (cell). A cylindrical solid load (Teflon, 3 mm height)
was put on the dry SAP particles while it could be freely slipped in the cell.
Desired load was placed on the SAP sample (Fig. 2.6). The saline solution
(0.9% NaCl) was then added until the liquid level was equal the height of
the sintered glass filter. The whole set was covered to prevent surface
evaporation and probable change in the saline concentration. After one
hour, the swollen particles were weighed again, and AUL was calculated
using equation (2).

50
Fig. 2.6 : A typical AUL tester picture and various parts [33].

51
Absorbency Under Load Test (AUL)
Table 2.6.1: AUL results of PAA-AS.
Table 2.6.2: AUL results of PAA-EAS.
EAS. Cross-linking
agent (%)
Weight of SAP
sample (g)
Weight of
swelled SAP (g)
AUL
g liquid/g SAP
4.0
2.0
1.5
1.0
0.5
0.1000
0.1000
0.1000
0.1000
0.1000
5.921
5.888
6.291
6.492
5.888
59.21
58.88
62.91
64.92
58.88
AS. cross-linking
agent (%)
Weight of SAP
sample (g)
Weight of
swelled SAP (g)
AUL
g Liquid/g SAP
4.0
2.0
1.5
1.0
0.5
0.1000
0.1000
0.1000
0.1000
0.1000
1.734
1.992
2.190
2.474
2.663
17.34
19.93
21.93
24.73
26.63

52
Table 2.6.3: AUL results of PAA-1,4-BDGE.
1,4-BDGE. cross-
linking agent (%)
Weight of SAP
sample (g)
Weight of
swelled SAP (g)
AUL
g liquid/g SAP
4.0
2.0
1.5
1.0
0.5
0.1000
0.1000
0.1000
0.1000
0.1000
2.603
2.612
2.623
2.648
2.721
26.03
26.12
26.23
26.48
27.21
Table 2.6.4: AUL results of PAA-EGDA.
EGDA. Cross-linking
agent (%)
Weight of SAP
sample (g)
Weight of
swelled SAP (g)
AUL
g liquid/g SAP
4.0
2.0
1.5
1.0
0.5
0.1000
0.1000
0.1000
0.1000
0.1000
1.688
3.163
3.072
3.436
3.467
16.88
31.63
30.72
34.36
34.67
2.7 pH Neutrality after swelling in water
Powder of each SAP (1 g) with 4% cross-linking percentage was
suspended into 100 ml de-ionized water. The mixture was stirred for about
10 minutes, and then the pH values were measured using a pH-meter.
Results are shown in the following table:

53
Table 2.7: pH of superabsorbent polymers.
Superabsorbent polymer pH
PAA-AS 6.2
PAA-EAS 5.92
PAA-EGDA 5.45
PAA-1,4-BDGE 5.28
2.8 Rewetting of SAP in water.
SAP (0.1 g) sample ( W0 ) was placed in a tea bag, then tea bag was
dipped in an excess amount of water solution for one hour to reach the
equilibrium swelling. Then excess solution was removed by hanging bag
until no liquid was dropped off. The tea bag was weighed (W1 ) and the
swelling capacity was calculated. Then bag was dried for three days and
SAP was heated until returned to initial weight and bag test applied again
and the results showed that no loss in absorbency of the polymer.
2.9 Rewetting of SAP in saline.
SAP (0.1 g) sample ( W0 ) was placed in a tea bag, then tea bag was
dipped in an excess amount of 0.95% saline solution for one hour to reach
the equilibrium swelling. Then excess solution was removed by hanging
bag until no liquid was dropped off. The tea bag was weighed (W1 ) and
the swelling capacity was calculated. Then bag was dried for three days and

54
SAP was heated until returned to initial weight and bag test applied again
and the results showed that no loss in absorbency of the polymer.
2.10 Polymer Extracts
To 250 ml Erlenmeyer flask containing 20 ml ethanol and 1g (W1) of
each SAP (4%) was poured with stirring for one hour, then SAP was
collected by filtration, dried and weight (W2), then % extract was
calculated.
Table 2.10: Percentage of SAP extracts.
SAP with 4%
cross-linker
Weight of SAP before
extraction (g)
Weight of SAP after
extraction (g)
% extraction
AS. 1.05 1.05 0 %
EAS. 0.9775 0.9782 0.07 %
1,4-BDGE. 0.9904 0.9907 0.03 %
EGDA. 0.9641 0.9643 0.02 %

55
2.11 Biodegradability
2.11.1Test Microorganisms
The organisms used for the degradation experiments were
Pseudomonas aeruginosa and Trichophyton rubrum.
Pseudomonas aeruginosa isolate was maintained on Nutrient Agar
(NA) (Oxoid) plates and incubated for 48 hours at 37C˚ prior to use.
Trichophyton rubrum was isolated from superficial skin of human
dermatomycoses patients. The isolated fungal isolate was maintained on
Sabouraud Dextrose Agar (SDA).
2.11.2 Biodegradation Experiments
Biodegradation experiment was performed using the plate assay,
which detects polymer -degrading activity based on the formation of a clear
zone surrounding the fungal colonies or growth of bacterial isolates as clear
colonies on media with the polymer as a sole carbon source [54].
The assay medium used in the study was Mineral salt media (MSM).
The MSM per 1000 mL distilled water was prepared as follows: K2HPO4,
1 g; KH2PO4, 0.2 g; NaCl, 1 g; CaCl2.2H2O, 0.002 g; boric acid, 0.005 g;
(NH4) 2SO4, 1 g; MgSO4.7H2O, 0.5 g; CuSO4.5H2O, 0.001 g; ZnSO4.7H2O,
0.001 g; MnSO4.H2O, 0.001 g and FeSO4.7H2O.

56
Fungal biodegradation experiment was screened using MSM
containing 0.5% (w/v) of the polymer either allyl sucrose or epoxy sucrose
as a sole carbon source, which was solidified with 1% agar at pH 6.0.
For bacterial biodegradation, the MSM containing about 0.5% (w/v)
of dry polymer (either Allyl sucrose or Epoxy sucrose) as a sole carbon
source and solidified with 2% agar at pH 7.0 was used.
After autoclaving, the media were poured into plates and allowing
the agar to set, a loopful of the bacterium or fungal strain were then
inoculated on the agar and the inoculated plates were sealed with parafilm.
The plates inoculated with bacteria were incubated at 37 Co
for seven days
under aerobic conditions. Plates inoculated with fungi were incubated at
room temperature for 1-3 weeks [54].
Fig. 2.11.2. Plate assay to visualize biodegradation of Allyl sucrose and Epoxy allyl sucrose by
Pseudomonas aeruginosa and Trichophyton rubrum. A-1, biodegradation of Allyl sucrose by
Pseudomonas aeruginosa; A-2, biodegradation of Epoxy allyl sucrose by Pseudomonas
aeruginosa; B-1, biodegradation of Allyl sucrose by Trichophyton rubrum; B-2 biodegradation
of Epoxy allyl sucrose by Trichophyton rubrum.

57
Chapter Three
Results and Discussion
The most abundant pure organic chemical in the world is sucrose. As
shown in Fig. 3 (structure and 1
H-NMR of sucrose), sucrose consists of two
monosaccharides, namely glucose (C-1 to C-6) and fructose (C-1' and C-
6'), positions 1', 6, and 6' contain primary hydroxyl group, whereas the rest
of hydroxyl groups are secondary [55].
The structure and conformation of sucrose was determined by X-ray
crystallography, and 1
H and 13
C-NMR. The primary hydroxyl group in
sucrose are sterically nonequivalent, and afford the opportunity to
selectively manipulate them. It is known that the 6 and 6' ends are more
reactive than the neopentyl 1' end. The reactivity trend among primary
hydroxyl groups in sucrose is different when sucrose is subjected to
acetylation with enzyme. The overall reactivity patterns of hydroxyl groups
in sucrose may be roughly put in the following order OH-6 = OH-6'>OH-
1'>OH at 2,3,3',4' >OH-4 [56].

58
O
OH
HO OH
O
O
OH
OH
OH
OH
HO
Sucrose
1
234
5
6 1'
2'
3'
4'
5'
6'
Fig 3: The chemical structure and 1
H-NMR of sucrose.
The potential value of sucrose as a raw material has been recognized
for many years and has been the subject of considerable research.
Although relatively few successful derivatives of sucrose have been
commercialized, there has been substantial interest in developing sugar-
based polymers with commercial values. Sucrose is a particularly
appropriate material for use in the formation of speciality polymers and
monomers produced currently from petroleum-based materials since it is:

59
(a) Naturally occurring and relatively inexpensive material;
(b)It is polyfunctional with three reactive primary alcohols that can
readily be derivatized (Fig.3) ;
(c) It is a non-reducing sugar and thus does not have the potential for the
wide variety of side-reactions that reducing sugars have; and
(d)It has a relatively easily hydrolyzed glycosidic linkage that allows
sucrose polymers to be potentially more biodegradable than
polymers made with other carbohydrates.
Sugar-based polymers are not entirely new. For example, a major
investigator was carried out on synthesis, characterization, and applications
of sucrose-based epoxy materials developed at USDA laboratories (New
Orleans, LA). It has been shown that: a) Sucrose can be converted into
epoxy in two steps process in over 85% overall yield using commercial
available reagents and solvents that could be recycled at low cost; and b)
the developed epoxy material is useful in creating new class of super-
adhesives [57].
Sucrose is a particularly appropriate material for use in the formation
of etherified products produced currently made from petroleum-based
materials [58]. The usual technique for the synthesis of carbohydrate ethers
involves a reaction of the carbohydrate with alkyl halides in a basic organic
solvent or aqueous solvent (O-alkylation reactions). Partial O-alkylation of

60
sucrose occurs in aqueous alkali upon treatment with alkylating agent at
about 100 Co
. However, octa-o-alkylation results when the pressure is
raised to about 500 psi. Selective methylation of sucrose could be obtained
using diazomethane in the presence of Lewis acids in methylene chloride
[59]. Treatment of sucrose with ethylene oxide or propylene oxide in the
presence of aqueous sodium hydroxide results in formation of octa-O-
hydroxyethyl and octa-O-hydroxypropyl sucrose respectively [60]. The
reaction of sucrose with epichlorohydrin results in the formation of
polyether polyols and glycidyl sucrose monomers. Penta-O-alkyl
derivatives of sucrose can be synthesized in high yields by use of
protecting group strategies such as 1', 6, 6'-tri Otritylation. Followed by
penta-O-alkylation and detritylation. Octa-O-alkylation could be conducted
by use of hydride bases in polar aprotic solvents, followed by addition of
alkyl halides [61].
In this research we were concerned about preparing polymerizable
monomers from sugar, sugar with unsaturated functional group that
undergoes polymerization in the presence of free radical initiator [62].
Then use the monomers for making biodegradable sugar based
superabsorbent polymers. The reason behind choosing sugar is mentioned
earlier in this section, it is the most abundant pure natural organic
chemical, available at low cost, hydrophilic, and biodegradable. Two
polymerizable sugar monomers were synthesized, they are allyl sucrose
and epoxy allyl sucrose [63].

61
3.1 Monomer Characterization
The allyl sucrose monomers produced in accordance with previous
methods are characterized by chromatography, and one-dimensional NMR
techniques proton and carbon-13, and IR.
3.1.1 1
H- NMR Spectroscopy of Allyl Sucrose (AS)
1
H-NMR for Allyl sucrose is shown in Fig. 3.1.1 (CDCl3) δ ppm):
3.26-4.28 sucrose[s] hydrogens; 5.23 Ha of the glucopyranosyl moieties;
5.24 (geminal terminal olefin hydrogens, Hb), 5.89 internal olefin Hc).
Fig. 3.1.1: 1H-NMR of Allyl Sucrose.

62
3.1.2 13
C-NMR Spectroscopy of Allyl Sucrose:
13
C-NMR of allyl sucrose is shown in Fig. 3.1.2, δ ppm): 68.23-88.70;
104.13-104.44 (C-3 resonances of the fructofuranosyl moieties of allyl
sucrose); 118 (CH2-1 vinyl), 135.21 (CH2-2 vinyl).
Fig. 3.1.2: 13
C-NMR of Allyl Sucrose.
3.1.3 1
H- NMR Spectroscopy of Epoxy Allyl Sucrose (EAS)
The 1
H-NMR for epoxy allyl sucrose (EAS) (CDCl3) is shown in
Fig.3.1.3, 2.67 (H-c, geminal methylene of the epoxy group) 3.0-4.3
(sucrose protons and methylenes), 4.82-4.98 (residual geminal terminal
olefin hydrogens), 5.55 (H-1 signal of the glucopyranosyl moieties of the
epoxy methallyl sucrose isomers).

63
Fig. 3.1.3: 1
H- NMR of Epoxy Allyl Sucrose
3.1.4 13
C-NMR Spectroscopy of Epoxy Allyl Sucrose
13
C-NMR for epoxy sucrose (CDCl3) is shown in Fig. 3.1.4, δ ppm):
19.24 (residual allylic CH3-d,), 51.5 (terminal epoxy allyl carbon CH2-c′),
56.1 (internal epoxy allyl carbon C-b′) 66 to 86 (sucroses carbons and
methylenes CH2), 89.6 (C-1 resonances of the glucopyranosyl moieties of
the epoxy allyl sucrose), 104.2 (C-2′ resonances of the fructofuranosyl
moieties of epoxy allyl sucrose isomers) and 105 (C-2′ residual resonances
of the fructofuranosyl moieties of unepoxidized methallyl sucrose isomers),
111.7 (residual CH2-c), 141.3 (residual tetrasubstituted olefin carbons C-b).

64
Fig. 3.1.4: 13
C-NMR of Epoxy Allyl Sucrose.
3.2 Discussion of prepared polymers
The prepared monomers in addition to other commercial monomer
were used as cross-linking agents for polymer prepared from polyacrylic
acid. Some of the chosen commercial monomers we never used as cross-
linking agents for polyacrylic acid.
3.2.1 Polyacrylic Acid cross-linked with Allyl Sucrose (PAA-AS).
Polyacrylic acid was polymerized in presence of various amounts of
AS. The polymerization was performed in presence of free radical initiator
sodium persulfate (Na2S2O8) under an inert atmosphere (N2). First, the

65
reaction was heated at low temperature (about 60 Co
) once the exothermic
reaction started, the heat was turned off, and the reaction continued for
about two hours. The produced solid mass was dried and grinded into
powder for evaluation. The general reaction for polymerizing acrylic acid
in presence of cross-linking agent allyl sucrose is shown in Fig. 3.2.1. The
procedure was performed on partially neutralized acrylic acid and on
another reaction neutralization was performed after polymerization.
The neutralization was performed by treating the polymer or the
monomer (AA) with a solution of sodium hydroxide to a pH of about 6.0.
In this reaction a radical is expected to be developed on both AS and AA
and that causes chain growth polymerization to occur and where the sugar
molecule forms like a bridge connecting the polyacrylic acid chains which
resulted in formation of a net work polymer as shown in Fig. 3.2.1.
O
O
O OH
O
O
OH
O
OH
OH
HO
O
O
O OH
O
O
OH
O
OH
OH
HO
CO2
-
CO2
-
CO2
-
CO2
-
CO2
-
CO2
-
CO2
-
CO2
-
CO2
-
O
O-
Na2S2O8
Fig. 3.2.1: Polymerization of acrylic acid in presence of crosslinker AS.

66
3.2.2 Polyacrylic Acid cross-linked with Epoxy Allyl Sucrose (PAA-
EAS).
EAS. The polymerization was performed in presence of free radical
initiator sodium persulfate (Na2S2O8) under an inert atmosphere (N2). First,
the reaction was heated at low temperature (about 60 Co
) once the
exothermic reaction started, the heat was turned off, and the reaction
continued for about two hours. The produced solid mass was dried and
grinded into powder for evaluation. The general reaction for polymerizing
acrylic acid in presence of cross-linking agent epoxy allyl sucrose is shown
in Fig. 3.2.2. The procedure was performed on partially neutralized acrylic
acid and on another reaction neutralization was performed after
polymerization. The neutralization was performed by treating the polymer
or the monomer (AA) with a solution of sodium hydroxide to a pH of about
6.0.

67
O
+
Na-
O
Initiator
O
O
OHO
O
O
HO
O
HO
HO
OH
OH
-
O
-
O
O O- O
O-
O O O O-
O-
O
-
O
O
-
O
O
-
OOO
-
O O
O O- O
O-
O O- O O O-
O-
O
O
OHO
O
O
HO
O
HO
HO
OH
O
O
O
O
O
OHO
O
O
HO
O
HO
HO
OH
O
O
O
O
O
O
OHO
O
O
HO
O
HO
HO
OH
OH
-
O
-
O
O O- O
O-
O O O O-
O-
O
-
O
O
-
O
O
-
OOO
-
O O
O
OH OH
Fig.3.2.2: Polymerization of acrylic acid with cross-linking agent EAS.
3.2.3 Polyacrylic Acid cross-linked with 1,4-Butanediol Diglycidyl
Ether (PAA-1, 4-BDGE).
1,4-BDGE. The polymerization was performed in presence of free radical
initiator sodium persulfate (Na2S2O8) under an inert atmosphere (N2). First ,
the reaction was heated at low temperature (about 60 Co
) once the
exothermic reaction started, the heat was turned off, and the reaction
acrylic acid in presence of cross-linking agent 1,4-BDGE is shown in
Fig.3.2.3. The procedure was performed on partially neutralized acrylic
acid and on other reactions neutralization was performed after

68
polymerization. The neutralization was performed by treating the polymer
or the monomer (AA) with a solution of sodium hydroxide to a pH of about
6.0.
Fig. 3.2.3: Polyacrylic acid cross-linked with 1,4-BDGE.
3.2.4 Polyacrylic Acid cross-linked with Ethylene Glycol Diacrylate
(PAA-EGDA).
Polyacrylic acid was also polymerized in presence of various
amounts of EGDA. The polymerization was performed in presence of free
radical initiator sodium persulfate (Na2S2O8) under an inert atmosphere
(N2). First, the reaction was heated at low temperature (about 60 o
C) once
the exothermic reaction started the heat was turned off, and the reaction

69
acrylic acid in presence of cross-linking agent EGDA is shown in Fig.3.2.4.
The procedure was performed on partially neutralized acrylic acid and in
other reactions neutralization was performed after polymerization. The
neutralization was performed by treating the polymer or the monomer (AA)
with a solution of sodium hydroxide to a pH of about 6.0. SAP polymer
produced with this was used as reference since it is known and well
documented.
-
O2C
-
O2C
-
O2C
O
O-
Na2S2O8
-
O2C
-
O2C
-
O2C
CO2
-
CO2
-
CO2
-
CO2
-
CO2
-
CO2
-
-
O2C
-
O2C
-
O2C
-
O2C
-
O2C
-
O2C
CO2
-
CO2
-
CO2
-
CO2
-
CO2
-
CO2
-
ethylene glycol diacrylate
O
O
O
O
O
O
O
O
O
O
O
O
Fig.3.2.4: Polyacrylic acid cross-linked with EGDA.

70
3.3 Polymer Analysis
Analysis of synthesized polymers were performed various techniques
such as IR, scanning electronic microscope (SEM), and differential
scanning calorimeter (DSC).
3.3.1 Infrared Spectra (IR) Results:
IR spectra of samples as KBr pellets were taken using a Nicolet 560
spectrometer (Nicolet Co., USA).
The IR of the three polymers made from acrylic acid and cross-
linking agents are shown in Fig. 3.3.1. Individual IR spectra are shown in
the appendix (figures a1, a2 and a3). As can be seen from Fig. 3.3.1, the
three spectra show that the main characteristic peaks at 3350 cm-1
(O-H
stretch), and 2906 cm-1
(C-H stretch). The small peaks at 1639 cm-1
result
from –C=O stretching. The absorption bands at 1372 cm-1
and 898 cm-1
are
ascribed to C-H bending vibration. The peak at 1318 cm-1
is attributed to
O-H bending vibration. Furthermore, the bands at 1556 and 1407
correspond to the carbonyl band.

71
1120
1172
1323
1407
1453
1556
1652
2949
3349
Metha
Allyl
Epox y
-0.10
-0.08
-0.06
-0.04
-0.02
0.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
0.16
Absorbance
100015002000250030003500
Wavenumbers (cm-1)
Fig. 3.3.1: IR for three of the prepared SAPs.
3.3.2 DSC Results:
The cross-linking was also supported by DSC analysis, as shown in
Fig. 3.3.7. DSC of SAP cross-linked with AS shows a weight loss in two
stages. The first stage ranged between 40 and 70 Co
and showed about
2.5% loss in weight, this may be due to the loss of absorbed and bound
water. The second stage of weight loss started at 130 Co
and continued to
210 Co
, during which 78% weight loss may correspond to the degradation
of cross-linker.
3.3.3 Morphological Analysis
SEM micrographs of prepared superabsorbent polymers are shown in
Fig.3.3.3. The differences are obvious. The conventional superabsorbent
polymer made from acrylic acid and EGDA cross-linking agent (Fig.
3.3.3.C) has a solid smooth non porous surface. While the other two

72
superabsorbent polymers made from acrylic acids and sugar monomers AS
and EAS show some porosity, highest porosity could be seen clearly from
the monograph of superabsorbent polymer cross-linked with EAS, the
pores are connected with each other. The porosity can clearly be seen in the
enlarged view (Fig. 3.3.3. B).
Fig. 3.3.3: SEM micrographs of prepared SAP’s: A is for superabsorbent polymer cross-linked
with 5% AS (PAA-AS) x1000; B is for superabsorbent polymer cross-linked with 5% EAS
(PAA-EAS) x500; B is for superabsorbent polymer cross-linked with 5% EAS (PAA-EAS)
x1000. C is for superabsorbent polymer cross-linked with 5% EGDA (PAA-EGDA) x1000.
A B
B
2
2
C

73
3.3.4: Superabsorbent Polymer Absorbency
Desired features of superabsorbent polymers are high swelling
capacity, high swelling rate and high strength of the swollen gel. These
properties make SAP’s ideal for use as mentioned in the introduction in
water absorbing applications such as disposable diapers, feminine napkins,
and agriculture, cosmetic and absorbent pads. The absorbency of the
prepared polymer for water and saline solution was evaluated. Results are
summarized in tables 3.3.4.1, 3.3.4.2, 3.3.4.3 and 3.3.4.4, and in graphs
3.3.4.1, 2, 3, and 4. The absorbency of prepared SAP’s in water was
measured using tea bag test. In this test about 0.1g of polymer is placed in
a pre-weighed tea bag and immersed in water for one hour. Then hanged
for one minute to remove unabsorbed water and its mass is determined.
The absorbency of polymers evaluated using this test is listed in the tables
as free swell g water/g SAP. As shown in the tables and graphs the free
swell increases by decreasing the percentage the cross-linker in all cases.
Polymer cross-linked with EAS showed the highest absorbency at
percentage of 0.5% was about 57 g water/ g SAP. The high absorbency of
PAA-EAS could be attributed to the high polarity of the polymer. PAA-
1,4-BDGE showed the lowest absorbency since it has the longest
hydrophobic chain, which makes them least polar than other polymers.
The absorbency of the prepared polymers was also evaluated in saline
solution. The absorbency for all polymers were lower than that in water
due to presence of salt which is known to lower the absorbency. This has

74
been previous prepared. The presence of charges in the SAP structure
causes an osmotic pressure difference between the gel and the solvent
phase. This pressure difference produces a strong driving force to diffuse
solvent to the gel phase. The diffusion process continues until the osmotic
pressure difference becomes zero. The osmotic pressure difference is
reduced in salts solutions, which leads to less swelling in comparison with
distilled water [64].
The absorbency was also evaluated under load (0.3 PSI). This is an
important test since it gives an indication about the ability of the SAP to
absorb and retain liquid under load, which is important for most
commercial applications of SAP. Also gives an indication about the gel
strength (Swollen SAP) [65].
Table 3.3.4.1: Absorbency of PAA-AS.
% of Cross-
linker
Free
Swell
Absorbency under
load
Absorbency in
Saline
4.00 38.50 19.00 29
2.00 39.30 22.00 29.7
1.50 44.20 24.30 30.5
1.00 50.00 27.60 30.7
0.50 51.00 29.80 31.5

75
Absorbency of SAP with Allyl Sucrose
0
10
20
30
40
50
60
4 2 1.5 1 0.5
% of Crosslinking Agent
Absorbencyg/gsolvent
Free Swell
Absorbency under load
Absorbency in Saline
Graph 3.3.4.1: Absorbency of PAA-AS.
Table 3.3.4.2: Absorbency of PAA-EAS.
% of Cross-
linker
Free
Swell
Absorbency
under load
Absorbency in
Saline
4.00 41.8 69.3 32.0
2.00 48.9 68.9 35.1
1.50 52 73.7 35.1
1.00 56.6 76.1 35.6
0.50 56.6 78.9 35.5

76
Absorbency of SAP with Epoxy Sucrose
0
10
20
30
40
50
60
70
80
90
4 2 1.5 1 0.5
% of Crosslinkung Agent
Absorbencyg/gSolvent
Free Swell
Graph 3.3.4.2: Absorbency of PAA-EAS.
Table3.3.4.3: Absorbency of PAA-EGDA.
% of Cross-
linker
Free
Swell
Absorbency under
load
Absorbency in
Saline
4.00 43.2 20.9 31.4
2.00 44.1 40.3 30.4
1.50 46.9 39.1 33.4
1.00 54.8 43.9 33.5
0.50 54.5 44.3 36

77
Absorbency of SAP with Ethylene Glycol Dimethylacrylate
0
10
20
30
40
50
60
4 2 1.5 1 0.5
%of Crosslinking Agent
Free Swell
Graph 3.3.4.3: Absorbency of PAA-EGDA.
Table 3.3.4.4: Absorbency of PAA-1,4-BDGE.
% of Cross-
linker
Free
Swell
Absorbency
under load
Absorbency in
Saline
4.00 35.9 27.5 26.6
2.00 36.4 27.6 24.3
1.50 38.9 27.8 27.4
1.00 41.5 28 27.5
0.50 38.7 28.8 29.4

78
Absorbency of SAP with 1,4-butanediol diglycidyl ether
0
5
10
15
20
25
30
35
40
45
4 2 1.5 1 0.5
% of Crosslinking Agent
Free Swell
Graph 3.3.4.4: Absorbency of PAA-1,4-BDGE.
3.3.5 Rewetting of Superabsorbent Polymers
Rewetting is a test used to evaluate the ability of superabsorbent
polymer to re-absorb after is being saturated with liquid and dried. The
rewetting property of the prepared SAP’s were evaluated, results showed
that no loss in absorbency of the polymer upon wetting, drying and then
rewetting.
3.3.6 pH Neutrality of SAP’s after swelling in water 4% cross-linking
In this test, SAP is suspended in certain volume of distilled water
(see experimental part), mixed for few minutes, then pH is measured.
Results of this test are summarized in Table 3.3.6. As shown in table, pH
of all SAP are close to neutral. Which is important for certain application
especially those where SAP gets in contact with human skin.

79
Table 3.3.6: pH of prepared superabsorbent polymers.
No. SAP pH
1 PAA-AS 6.2
2 PAA-EAS 5.92
3 PAA-EGDA 5.45
4 PAA-1,4-BDGE. 5.28
3.3.7 Thermal stability of prepared Superabsorbent Polymers
TA Instruments (Newcastle, DE, 2920). DSC was used in these
experiments. A standard heating ramp of 28 Co
/min. was chosen and a
modulation period of 60 s and modulation temperature amplitude of 0.328
Co
was chosen based upon the recommended specifications. N2 purge was
used for all experiments. Baseline calibration was performed regularly with
empty pans at 2 and 108 Co
/min., and a four point temperature calibration
was performed with different metal standards.
Combustion took place under oxidative conditions within a
temperature range from 30 to 300 Co
, using a gas flow of 120 ml min.−1
(20% O2 / 80% He). The sample (16 mg) was combusted in an Al2O3 pan.
Self-controlled calibration was carried out. DSC curves were corrected by
subtracting the DSC curve of the empty pan from the recorded sample
curve. Thermograms produced by DSC analysis of prepared polymers are
shown in Fig.3.3.7: PAA-EAS showed the highest stability. PAA-EAS

80
Polymer degradation started at about 195 Co
. The lowest stability was
shown by PAA-EGDA polymer which starts degrading at 170 Co
. All
samples showed two peaks at about 50-55 Co
and 150-155 Co
, which
could be related to decomposition or melting side products produced during
polymerization such formation of dimmers or evaporation of solvent.

81
Fig.3.3.7: DSC for prepared SAPs. (AS., EAS., 1,4-BDGE., EGDA.)

82
3.3.8 Polymer Extracts
Polymer extract is defined as the residual un-reacted monomers or
small chain polymer that present in superabsorbent polymer and soluble in
water or polar solvent such as ethanol. In this test a known weight of SAP
(W1) is suspended in 20 ml of ethanol and stirred for one hour as shown in
the experimental part. Then SAP is collected by filtration dried and weight
(W2). The % extract is calculated as shown in equation (3).
% extracts = [W2 - W1 /W1] x 100%
Table 3.3.8: SAP extract in prepared polymers.
SAP with 4%
cross-linker
Weight of SAP
before extraction (g)
Weight of SAP
after extraction (g)
% extraction
AS 1.05 1.05 0 %
EAS 0.9775 0.9782 0.07 %
1,4-BDGE 0.9904 0.9907 0.03 %
EGDA 0.9641 0.9643 0.02 %
As shown in table 3.3.8, the percent extract is close to zero in all prepared
polymers. Which indicate that no residual monomer is present, a property
that is crucial to several industrial application of SAP, especially those
where the SAP gets in contact with human skin.

83
3.4 Biodegradability
Prepared superabsorbent polymers specially those cross-linked with
sugar based monomers were subjected to biodegradability test using the
organism Pseudomonas aeruginosa and Trichophyton rubrum, which is
known to consume sugar molecules. The test was carried out as shown in
detail in the experimental part. Result showed that there is some bacteria
growth as can be seen in Fig.3.4. This is an indication that the cross-links
between the polymer chains that are made up from sugar monomers are
degrading and the polymers chains are breaking a part.
Fig. 3.4: Plate assay to visualize biodegradation of Allyl sucrose and Epoxy allyl sucrose by
Pseudomonas aeruginosa and Trichophyton rubrum. A-1, biodegradation of Allyl sucrose by
Pseudomonas aeruginosa; A-2, biodegradation of Epoxy allyl sucrose by Pseudomonas
aeruginosa; B-1, biodegradation of Allyl sucrose by Trichophyton rubrum; B-2 biodegradation
of Epoxy allyl sucrose by Trichophyton rubrum [33].

84
The organisms used for the degradation experiments were
Pseudomonas aeruginosa and Trichophyton rubrum.
Pseudomonas aeruginosa isolate was maintained on Nutrient Agar
(NA) (Oxoid) plates and incubated for 48 hours at 37 C˚ prior to use
Trichophyton rubrum was isolated from superficial skin of human
dermatomycosis patients. The isolated fungal was maintained on
Sabouraud Dextrose Agar (SDA).

85
CONCLUSION
1. Allyl Sucrose and Epoxy Allyl Sucrose were synthesized and
characterized by various spectroscopic techniques.
2. The prepared sucrose-based monomers were used as cross-linking agents
for superabsorbent polymers.
3. Four different superabsorbent polymers were synthesized and
characterized by IR, DSC, and SEM.
4. Two of the prepared superabsorbent polymers were cross-linked with
sucrose-based monomers AS and EAS, and the other two were cross
linked with 1,4-BDGE and EGDA.
5. The absorbent properties of the prepared superabsorbent polymers were
evaluated in water and in saline solution, results indicate that the SAP
cross-linked with EAS has the highest absorbent capacity and absorbency
under load. This could be because it has the highest polarity, highest
number of hydroxyl groups.
6. Superabsorbent polymers cross-linked with AS and EAS are
biodegradable as shown by the biodegradability test.
7. Superabsorbent polymers cross-linked with AS and EAS have an
economic advantages over conventional, petrochemical-derived SAP in
that they are biodegradable and prepared in one step process.

86
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